Premenopausal females tiave a lower incidence of many cardiovascular diseases, including iiypertension. Because this protection steeply declines after menopause, we know that estrogen is at least partially responsible for these beneficial effects. There are two known estrogen receptor subtypes that mediate the genomic actions of this hormone; however, it is not known whether the newly discovered G protein-coupled receptor 30 (GPR30) contributes to estrogen's cardiovascular effects. Using the mRen2.Lewis rat, a unique angiotensin ll-dependent, estrogen-sensitive, and salt-sensitive hypertensive model which appropriately reflects the higher blood pressure and salt-sensitivity seen in postmenopausal women, we showed that in vivo administration of the selective GPR30 agonist G-1 in ovariectomized females significantly reduces blood pressure, alters vascular gene expression of renin-angiotensin system components, and reduces angiotensin ll-induced vasoconstriction. We hypothesize that GPR30 exerts beneficial cardiovascular effects by opposing the actions of Ang II in vascular smooth muscle cells. Separating the actions of estrogen at GPR30 from those mediated by its nuclear estrogen receptors may elucidate the current controversy surrounding hormone replacement therapy. The proposal will take a comprehensive approach utilizing an in vitro cell culture system, an ex vivo isolated resistance vessel preparation, and in vivo analysis ofthe congenic mRen2.Lewis hypertensive animal to determine (1) whether GPR30 activation in mesenteric smooth muscle cells influences calcium mobilization; (2) whether gender and estrogen status regulates expression of GPR30 in the vasculature; (3) whether GPR30 influences the function of renin-angiotensin system components; and (4) whether a high salt diet alters vascular GPR30 expression and function. These studies will establish the regulation of'Vascular GPR30 expression and assess its acute and chronic interaction with the renin-angiotensin system.